Microelectromechanical system device

Abstract

A microelectromechanical system device includes a mirror structure, a frame, a first cantilever, and a second cantilever. The mirror structure is suspended in the frame by the first cantilever and the second cantilever. The first cantilever includes a first sub-cantilever connected to the frame, a second sub-cantilever connected to the mirror structure, and a third sub-cantilever connecting the first sub-cantilever and the second sub-cantilever. Each of the first sub-cantilever and the third sub-cantilever includes a first bottom electrode, a first piezoelectric layer on the first bottom electrode, and first and second electrodes on the first piezoelectric layer, where the first and second electrodes are separated from each other.

Description

Technical Field

[0001] The embodiments disclosed herein relate to microelectromechanical systems (MEMS) devices. Background Technology

[0002] Micro-mechanical systems (MEMS) devices are known to have mirror structures obtained using semiconductor material technology. For example, such MEMS devices are used in portable devices, such as portable computers, laptops, notebook computers (including ultra-thin notebooks), PDAs, tablet computers, mobile phones, or smartphones, for optical applications, particularly for guiding one or more beams of light radiation generated by a light source to a desired pattern and / or direction. Utility Model Content

[0003] In some embodiments of this disclosure, the microelectromechanical system (MEMS) device includes a mirror structure, a frame, a first cantilever, and a second cantilever. The mirror structure is suspended in the frame by the first and second cantilever arms. The first cantilever includes a first sub-cantilever connected to the frame; a second sub-cantilever connected to the mirror structure; and a third sub-cantilever connecting the first and second sub-cantilever arms. Each of the first and third sub-cantilever arms includes a first bottom electrode; a first piezoelectric layer on the first bottom electrode; and a first top electrode and a second top electrode on the first piezoelectric layer, wherein the first and second top electrodes are separated from each other.

[0004] In some embodiments of this disclosure, the microelectromechanical system device includes: a mirror structure; a frame; a first cantilever and a second cantilever, wherein the mirror structure is suspended in the frame by the first cantilever and the second cantilever, each of the first cantilever and the second cantilever including a bottom electrode, a piezoelectric layer above the bottom electrode, and a first top electrode and a second top electrode above the piezoelectric layer; a first connecting spring connecting the first cantilever to the mirror structure; and a second connecting spring connecting the second cantilever to the mirror structure.

[0005] In some embodiments of this disclosure, the microelectromechanical system (MEMS) device includes a substrate, a bottom electrode layer, a piezoelectric layer, a first top electrode, a second top electrode, and a mirror above the piezoelectric layer. The substrate has a first cantilever region, a second cantilever region, a mirror region, and a frame region, wherein the mirror region is suspended by the first cantilever region, the second cantilever region, and the frame region. The first cantilever region includes a first sub-cantilever region, a second sub-cantilever region, and a third sub-cantilever region, wherein the third sub-cantilever region connects to the mirror region. The bottom electrode layer is above the substrate. The piezoelectric layer is above the bottom electrode layer. The first top electrode, the second top electrode, and the mirror are above the piezoelectric layer. The mirror is located in the mirror region. A first portion of the first top electrode and a first portion of the second top electrode are located in the first sub-cantilever region, and a second portion of the first top electrode and a second portion of the second top electrode are located in the second sub-cantilever region. Attached Figure Description

[0006] The various aspects of this disclosure can be best understood in conjunction with the accompanying drawings and the following detailed description. Note that, in accordance with standard industry practice, the features are not drawn to scale. In fact, for clarity of discussion, the dimensions of the features may be arbitrarily increased or decreased.

[0007] Figure 1A and Figure 1B These are, respectively, top and bottom views of a microelectromechanical system (MEMS) device according to some embodiments of the present disclosure;

[0008] Figure 1C For along Figure 1A and Figure 1B Cross-sectional views of the MEMS device taken by lines AA and BB in the diagram;

[0009] Figure 1D For along Figure 1A and Figure 1B A cross-sectional view of the MEMS device taken along the rotation axis AX;

[0010] Figure 1E for Figure 1A A magnified view of a portion;

[0011] Figures 2 to 9 This is a cross-sectional view of an intermediate stage in the formation of a MEMS device according to some embodiments of this disclosure;

[0012] Figure 10A and Figure 10B These are top and bottom views of a MEMS device according to some embodiments of the present disclosure;

[0013] Figure 11A and Figure 11B These are top and bottom views of a MEMS device according to some embodiments of the present disclosure;

[0014] Figure 12A and Figure 12B These are top and bottom views of a MEMS device according to some embodiments of the present disclosure.

[0015] [Symbol Explanation]

[0016] 110: Semiconductor substrate

[0017] 112: Substrate

[0018] 112F: Frame

[0019] 114: Dielectric layer

[0020] 116: Semiconductor layer

[0021] 120: Dielectric layer

[0022] 130: Electrode layer

[0023] 140: Piezoelectric layer

[0024] 140O: Opening

[0025] 150: Second electrode layer

[0026] 152, 154, 156, 158: Electrodes

[0027] 160: Back metal layer

[0028] 170: Rib structure

[0029] AA, BB, CC: lines

[0030] AD: Direction

[0031] AX: Rotation axis

[0032] CA: Cantilever area

[0033] CA', CB': Cantilever area

[0034] CA1~CA5, CA1'~CA3', CB1~CB5, CB1'~CB3': Sub-cantilever region

[0035] CB: Cantilever area

[0036] D1, D2: Vertical direction

[0037] FR: Frame area

[0038] MR: Mirror area

[0039] O1, O2, O3, OA, OB, OC: Openings

[0040] SB1, SB2: Shock buffer zones

[0041] SPA1, SPA2, SPB1, SPB2, SPB1': Connecting areas Detailed Implementation

[0042] The following disclosure provides numerous different embodiments or instances for implementing various features of the provided subject matter. Specific examples of components and arrangements described below are used to simplify this disclosure. Of course, these are merely examples and are not intended to be limiting. For example, the following description of forming a first feature above or on a second feature may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which an additional feature is formed between the first and second features such that the first and second features do not need to be in direct contact. Furthermore, element symbols or letters may be repeated in various instances of this disclosure. This repetition is for simplicity and clarity and does not in itself specify a relationship between the various embodiments or configurations discussed.

[0043] Furthermore, for ease of description, spatial relative terms such as “below,” “under,” “below,” “above,” and “above” may be used herein to describe the relationship between one element or feature and another, as illustrated in the accompanying drawings. In addition to the orientations depicted in the drawings, spatial relative terms are intended to cover different orientations of the device during use or operation. The device may be oriented in other ways (rotated 90 degrees or otherwise), and the spatial relative descriptive terms used herein shall be interpreted accordingly. As used herein, “around,” “about,” “approximately,” or “substantially” generally refers to within 20%, 10%, or 5% of a given value or range. The numerical approximations given herein mean that, unless explicitly stated otherwise, the terms “around,” “about,” “approximately,” or “substantially” can be inferred.

[0044] LiDAR (Light Detection and Ranging) has been widely applied in various fields, such as topography, 3D imaging, and spectroscopy. In recent years, LiDAR has received considerable attention in the automotive industry as a key component of advanced autonomous driving systems. Compared to other autonomous driving sensor technologies (such as radar and stereo cameras), LiDAR offers the advantage of providing high-precision and high-resolution 3D ambient measurement in harsh environments. Microelectromechanical system (MEMS) LiDAR offers advantages such as low mass production cost, high operating frequency, high resolution, and low power consumption. Piezoelectric MEMS LiDAR further offers advantages such as low power consumption, small size, and high production capacity.

[0045] Figure 1A and Figure 1B The images shown are a top view and a bottom view of a microelectromechanical system (MEMS) device according to some embodiments of the present disclosure. Figure 1C For along Figure 1A and Figure 1B The cross-sectional view of the MEMS device taken by the AA and BB lines. Figure 1D For along Figure 1A and Figure 1B A cross-sectional view of the MEMS device taken from the rotation axis AX. The MEMS device includes a frame 112F, a dielectric layer 114, a semiconductor layer 116, a dielectric layer 120, a first electrode layer 130, a piezoelectric layer 140, a second electrode layer 150, a back metal layer 160, and a rib structure 170. The dielectric layer 114, semiconductor layer 116, dielectric layer 120, first electrode layer 130, piezoelectric layer 140, and second electrode layer 150 are supported by the frame 112F. The second electrode layer 150 has separate electrodes 152, 154, 156, and 158. In other words, electrodes 152, 154, 156, and 158 are electrically isolated from each other. The piezoelectric layer 140 is sandwiched between electrodes 152, 154, and 158 of the second electrode layer 150 and the first electrode layer 130. Electrodes 152, 154, and 158 are separate from the first electrode layer 130. Electrode 156 contacts the first electrode layer 130 and serves as a conductive path / pad for the first electrode layer 130. A back metal layer 160 is formed on the back side of the frame 112F.

[0046] exist Figure 1A and Figure 1BIn this context, the MEMS device may include a first cantilever region CA, a second cantilever region CB, a mirror region MR, impact buffer regions SB1 and SB2, and a frame region FR. The mirror region MR is suspended, for example, separated from the frame region FR by the first cantilever region CA, the second cantilever region CB, and the impact buffer regions SB1 and SB2. Electrode 158 may be located in the mirror region MR and function as a reflector, wherein the reflector (i.e., electrode 158) is laterally aligned with electrodes 152 and 154. The mirror region MR is rotatable along the rotation axis AX. In this context, the first cantilever region CA, the second cantilever region CB, the mirror region MR, the impact buffer regions SB1 and SB2, and the frame region FR may be referred to as the first cantilever, the second cantilever, the mirror structure, the impact buffer, and the frame, respectively.

[0047] In this embodiment, impact buffer regions SB1 and SB2 connect both ends of the mirror region MR to the frame region FR along the rotation axis AX, thereby enhancing the stability of the device and reducing swaying. The frame region FR can serve as an anchor for the mirror region MR via the impact buffer regions SB1 and SB2. The impact buffer regions SB1 and SB2 can extend into an elongated shape along the rotation axis AX. Each impact buffer region SB1 and SB2 has a first end connected to the mirror region MR and a second end connected to the frame region FR, and the first and second ends of the impact buffer regions SB1 and SB2 are arranged along the rotation axis AX. The impact buffer can increase the stability of the reflective mirror and reduce swaying. In some embodiments, the width of the impact buffer regions SB1 and SB2 can increase from the mirror region MR to the frame region FR.

[0048] The first cantilever region CA and the second cantilever region CB can function as actuators that deform and provide a driving force to rotate the mirror when voltage is applied to electrodes 152, 154, and 156. Each of the first cantilever region CA and the second cantilever region CB has a first end connected to the frame 112F and a second end connected to the mirror region MR. The MEMS device may further include connection regions SPA1 and SPA2 located between the mirror region MR and the first cantilever region CA, and connection regions SPB1 and SPB2 located between the mirror region MR and the second cantilever region CB. Connection regions SPA1 and SPA2 are spaced apart from the rotation axis AX. Connection regions SPA1 and SPA2 and shock buffer regions SB1 and SB2 are unaffected by the second electrode layer 150, the piezoelectric layer 140, and the first electrode layer 130.

[0049] In the mirror region MR, a rib structure 170 is formed on the back side of the dielectric layer 114 to provide structural support for the mirror region MR, thereby maintaining the flatness of the mirror region MR. The rib structure 170 may be one or more rings, one or more straight lines, or a combination thereof. The overall size of the rib structure 170 is smaller than that of the mirror region MR.

[0050] Electrodes 152 and 154 can be located in the first cantilever region CA and the second cantilever region CB to provide vertical displacement by applying different voltage phases in different regions of the piezoelectric layer 140, thereby providing a (rotational / torsional) force to the mirror region MR. In other words, voltages with phase changes can be applied to electrodes 152 and 154 respectively to provide a (rotational / torsional) force to the mirror region MR. For example, a positive voltage can be applied to electrode 152 and a negative voltage to electrode 154. Alternatively, a positive voltage can be applied to electrode 154 and a negative voltage to electrode 152. Different voltages can be applied to electrodes 152 / 154 in the two cantilever regions CA and CB for individual operation and control.

[0051] Opening O1 can be located between the mirror region MR and the first cantilever region CA, and between the mirror region MR and the second cantilever region CB. Openings O2 and O3 can be located between the frame region FR and the first cantilever region CA, and between the frame region FR and the second cantilever region CB. Openings O1 and O3 restrict the connection areas (or connecting springs) SPA1 and SPA2 between the mirror region MR and the first cantilever region CA at two positions adjacent to the impact buffer regions SB1 and SB2, respectively, and restrict the connection areas (or connecting springs) SPB1 and SPB2 between the mirror region MR and the second cantilever region CB at two positions adjacent to the impact buffer regions SB1 and SB2, respectively. Openings O2 and O3 can be located between the frame region FR and the first cantilever region CA, and between the frame region FR and the second cantilever region CB. Openings O2 and O3 restrict the connection point between the frame region FR and the first cantilever region CA at two positions laterally aligned with the impact buffer regions SB1 and SB2, respectively, and restrict the connection point between the mirror region MR and the second cantilever region CB at two positions laterally aligned with the impact buffer regions SB1 and SB2, respectively.

[0052] In some embodiments of this example, openings O2 and O3 extend into the first cantilever region CA, such that the first cantilever region CA has sub-cantilever regions CA1 to CA5. Sub-cantilever region CA3 is connected to the mirror region MR, for example, via connecting regions (connecting springs) SPA1 and SPA2. Sub-cantilever regions CA1 and CA5 are respectively connected to the frame region FR. Sub-cantilever region CA2 connects sub-cantilever region CA1 to sub-cantilever region CA3, and sub-cantilever region CA4 connects sub-cantilever region CA5 to sub-cantilever region CA3. Each of the sub-cantilever regions CA1, CA2, CA4, and CA5 has two electrodes 152 and 154. Sub-cantilever region CA3 may extend into the mirror region MR in a direction parallel to the rotation axis AX of the mirror region MR. In the depicted embodiment, each sub-cantilever region CA3 has one electrode 154 and no electrode 152. In some other embodiments, each sub-cantilever region CA3 has one electrode 152 and no electrode 154. In some other embodiments, each sub-cantilever region CA3 may have two electrodes 152 and 154. Electrodes 152 of sub-cantilever regions CA1, CA2, CA4, and CA5 are electrically connected to each other, and electrodes 154 of sub-cantilever regions CA1–CA5 are electrically connected to each other. This configuration provides a larger vertical displacement by accumulating each bit displacement. Electrodes 152 and 154 may extend from the first cantilever region CA to the frame region FR, thereby serving as conductive paths / pads for electrical connections. Electrode 156 may be located in the frame region FR and serve as a conductive path / pad for the first electrode layer 130.

[0053] Similarly, in some embodiments of this example, openings O2 and O3 extend to the second cantilever region CB, such that the second cantilever region CB has sub-cantilever regions CB1 to CB5. Sub-cantilever region CB3 is connected to the mirror region MR, for example, via connecting regions (connecting springs) SPB1 and SPB2. Sub-cantilever regions CB1 and CB5 are respectively connected to the frame region FR. Sub-cantilever region CB2 connects sub-cantilever region CB1 to sub-cantilever region CB3, and sub-cantilever region CB4 connects sub-cantilever region CB5 to sub-cantilever region CB3. Each of the sub-cantilever regions CB1, CB2, CB4, and CB5 has two electrodes 152 and 154. Sub-cantilever region CB3 may extend to the mirror region MR in a direction parallel to the rotation axis AX of the mirror region MR. In the depicted embodiment, each sub-cantilever region CB3 has one electrode 154 and no electrode 152. In some other embodiments, each sub-cantilever region CB3 has one electrode 152 and no electrode 154. In some other embodiments, each sub-cantilever region CB3 may have two electrodes 152 and 154. Electrodes 152 of sub-cantilever regions CB1, CB2, CB4, and CB5 are electrically connected to each other, and electrodes 154 of sub-cantilever regions CB1–CB5 are electrically connected to each other. This configuration provides a larger vertical displacement by accumulating each bit displacement. Electrodes 152 and 154 may extend from the second cantilever region CB to the frame region FR, thereby serving as conductive paths / pads for electrical connections. In this case, sub-cantilever regions CA1–CA5 and CB1–CB5 may be referred to as sub-cantilevers.

[0054] In some embodiments of this disclosure, to increase vertical displacement, the sub-cantilever regions CA1, CA2, CA4, CA5 and / or sub-cantilever regions CB1, CB2, CB4, CB5 may have elongated shapes. The elongated shapes may extend along a direction AD orthogonal to the rotation axis AX. In some embodiments, the lengths of the sub-cantilever regions CA1, CA2, CA4, CA5 measured along direction AD may be greater than the lengths of the sub-cantilever regions CA1, CA2, CA4, CA5 measured along the rotation axis AX. In some embodiments, because the piezoelectric layer 140 exhibits anisotropic behavior during deformation when a voltage is applied, the elongated shapes in the sub-cantilever regions CA1, CA2, CA4, CA5 and / or sub-cantilever regions CB1, CB2, CB4, CB5 will result in different amounts of deformation along the rotation axis AX and in direction AD. Multi-cantilever (e.g., triple-cantilever) designs provide higher vertical displacement, ensuring good performance of the scanning mirror in terms of optical scanning angles. In some embodiments, the widths of the connecting regions SPA1 and SPA2 are smaller than the widths of the sub-cantilever regions CA1 to CA5 of the first cantilever region CA, and the widths of the connecting regions SPB1 and SPB2 are smaller than the widths of the sub-cantilever regions CB1 to CB5 of the second cantilever region CB.

[0055] Figure 1E for Figure 1A A magnified view of a portion. For example... Figure 1E As shown in the top view, the angle between the longitudinal direction of sub-cantilever regions CA1, CA2, CA4, CA5 and / or sub-cantilever regions CB1, CB2, CB4, CB5 and the direction AD perpendicular to the rotation axis AX of the mirror region MR is in the range of approximately 0 degrees to approximately 40 degrees. In some embodiments, the angle between the longitudinal direction D2 of sub-cantilever region CA2 and direction AD may be greater than the angle between the longitudinal direction D1 of sub-cantilever region CA1 and direction AD. For example, in the top view, the angle between the longitudinal direction D1 of sub-cantilever region CA1 and direction AD may be in the range of approximately 0 degrees to approximately 10 degrees, while in the top view, the angle between the longitudinal direction D2 of sub-cantilever region CA2 and direction AD may be in the range of approximately 10 degrees to approximately 20 degrees. Sub-cantilever regions CA4 and CA5 may have the same symmetrical configuration as sub-cantilever regions CA2 and CA1, and therefore will not be repeated here. Sub-cantilever regions CB1 to CB5 may have the same symmetrical configuration as sub-cantilever regions CA1 to CA5, and therefore will not be repeated here.

[0056] Figures 2 to 9 This is a cross-sectional view of an intermediate stage in the formation of a MEMS device according to some embodiments of this disclosure. Figure 2 , Figure 3 , Figure 4A , Figure 5A , Figure 6A and Figures 7 to 9 sectional view along Figure 1A and Figure 1B The AA and BB lines are taken from the middle. Figure 4B , Figure 5B and Figure 6B The sectional view is along Figure 1A and Figure 1B The rotation axis AX in the diagram is taken. It should be understood that in... Figures 2 to 9 Additional steps may be provided before, during, and after the steps shown, and some steps described below may replace or eliminate additional embodiments of the method. The order of operations / processes may be interchanged.

[0057] See Figure 2A semiconductor substrate 110 is provided. The semiconductor substrate 110 may be a semiconductor-on-insulator (SOI) substrate, including a substrate 112, a dielectric layer 114 on the substrate 112, and a semiconductor layer 116 on the dielectric layer 114. The substrate 112 may be a bulk substrate, such as a bulk silicon substrate. The substrate 112 may include silicon. Alternatively, the substrate 112 may include other basic semiconductors, such as germanium. The substrate 112 may also include compound semiconductors, such as silicon carbide, gallium arsenide, indium arsenide, and indium phosphide. The substrate 112 may include alloy semiconductors, such as silicon germanium, silicon germanium carbide, gallium arsenide phosphide, and gallium indium phosphide. In some embodiments, the substrate 112 may be referred to as a disposal wafer. The dielectric layer 114 may include silicon oxide or other suitable insulating materials and / or combinations thereof. In some embodiments, the dielectric layer 114 may include a buried oxide layer (BOX) grown or deposited on the silicon substrate 112. Semiconductor layer 116 may include basic semiconductors such as silicon (Si) or germanium (Ge) in a crystal structure; compound semiconductors such as silicon-germanium (SiGe), silicon carbide (SiC), gallium arsenide (GaAs), gallium phosphide (GaP), indium phosphide (InP), indium arsenide (InAs), and / or indium antimonide (InSb); or combinations thereof. For example, the SOI substrate is fabricated using separation by implantation of oxygen (SIMOX), wafer bonding, and / or other suitable methods. For clarity, in cross-sectional views of some embodiments, semiconductor substrate 110 is shown as including a first cantilever region CA, a second cantilever region CB, a mirror region MR, shock buffer regions SB1 and SB2, and a frame region FR, corresponding to… Figures 1A to 1D Examples of implementations.

[0058] A dielectric layer 120 is deposited on a semiconductor substrate 110. The dielectric layer 120 may be made of any suitable dielectric material, such as silicon oxide, silicon nitride, or a combination thereof.

[0059] Electrode layer 130 is deposited on dielectric layer 120. Electrode layer 130 may include suitable conductive materials, such as platinum, titanium, copper (Cu), gold (Au), or combinations thereof.

[0060] A piezoelectric layer 140 is deposited on the electrode layer 130. The piezoelectric layer 140 may include suitable piezoelectric materials, such as lead zirconate titanate (PZT), aluminum nitride (AlN), zinc oxide (ZnO), TiBaO3, potassium sodium niobate ((K,Na)NbO3, KNN)-based lead-free piezoelectric materials, or combinations thereof. By using a KNN-based lead-free piezoelectric material in the piezoelectric layer 140, the fabrication process of the piezoelectric layer 140 can be compatible with complementary metal-oxide-semiconductor (CMOS) processes, thereby maintaining good piezoelectric properties.

[0061] See Figure 3 The piezoelectric layer 140 is patterned to have one or more openings 140O, thereby exposing the underlying electrode layer 130. The patterning process may include forming a mask on the piezoelectric layer 140 by a suitable photolithography process, followed by a suitable etching process, such as wet etching.

[0062] See Figure 4A and Figure 4B The second electrode layer 150 is deposited on the piezoelectric layer 140 and patterned into electrodes 152, 154, 156, and 158 (see [reference]). Figures 1A to 1C The second electrode layer 150 may include a suitable conductive material, such as platinum, silver, copper (Cu), gold, chromium (Cr), or combinations thereof. In some embodiments, the conductive material of the second electrode layer 150 is selected to achieve high reflectivity within the operating wavelength range. The deposition process for the second electrode layer 150 may include an electron gun evaporation method. Patterning may include a lift-off process. After patterning, electrode 156 (see...) Figures 1A to 1C It can extend into the opening 140O in the piezoelectric layer 140.

[0063] See Figure 5A and Figure 5B The opening OA is etched in the piezoelectric layer 140, electrode layer 130, and dielectric layer 120. The etching process may include reactive-ion etching (RIE) processes, such as inductively coupled plasma (ICP) etching. After the etching process, the semiconductor layer 116 can remain substantially intact. The formation of the opening OA can remove material from the piezoelectric layer 140, electrode layer 130, and dielectric layer 120 from the connection regions SPA1, SPA2, SPB1, and SPB2, and the impact buffer regions SB1 and SB2.

[0064] See Figure 6A and Figure 6BThe opening OB is etched in the semiconductor layer 116 exposed by the opening OA. By forming the openings OA and OB, the first cantilever region CA, the second cantilever region CB, the mirror region MR, the impact buffer regions SB1 and SB2, the frame region FR, the connection regions SPA1 and SPA2, and the connection regions SPB1 and SPB2 are defined.

[0065] See Figure 7 A back metal layer 160 is deposited on the back side of the semiconductor substrate 110 and patterned to cover the frame region FR and expose other regions. The back metal layer 160 may include a suitable metal, such as aluminum (Al) or a combination thereof.

[0066] See Figure 8 A two-step etching process is performed to remove a portion of the substrate 112 exposed by the back metal layer 160, thereby leaving the frame 112F and the rib structure 170 on the back side of the dielectric layer 114. The two-step etching process may include a first dry etching process and a second dry etching process following the first dry etching process. A photomask defining the rib pattern may be formed on the back side of the substrate 112 via a photolithography process. The first dry etching process may form the rib pattern in the substrate 112 by etching the substrate 112 to an appropriate depth via the photomask. After the first dry etching process, the substrate 112 has a rib pattern on the back side of the dielectric layer 114. Subsequently, the photomask is removed by an appropriate stripping or ashing process. Then, a second dry etching process is performed to etch the substrate 112 using the back metal layer 160 as an etching mask until the dielectric layer 114 is exposed. For example, once the dielectric layer 114 is exposed, the second dry etching process terminates without completely removing the rib pattern, such that when the dielectric layer 114 is exposed, the remaining rib pattern forms the rib structure 170. In other words, the second dry etching process can etch back the rib pattern to form the rib structure 170 without using an additional photomask. The first and second dry etching processes can be RIE or other suitable etching processes.

[0067] See Figure 9 After forming the rib structure 170, the dielectric layer 114 is patterned using a back-side dry etching process. The patterning process may include forming a photomask using a photolithography process followed by etching. The patterning process may form openings OC in the dielectric layer 114. Openings OC may communicate with openings OB and OA, and their combination may be referred to as openings O1 and O2. Through this configuration, the mirror region MR is suspended, for example, separated from the frame region FR by a first cantilever region CA, a second cantilever region CB, and impact buffer regions SB1 and SB2.

[0068] Figure 10A and Figure 10BThese are top and bottom views of a MEMS device according to some embodiments of this disclosure. The details of this embodiment are similar. Figures 1A to 1C The difference shown in the details is that the MEMS device has four cantilever regions CA, CB, CA', CB', and each of the four cantilever regions CA, CB, CA', CB' can be used as an actuator that deforms and provides a driving force for driving the mirror when a voltage is applied to electrodes 152, 154, and 156.

[0069] In this embodiment, the cantilever region CA has sub-cantilever regions CA1 to CA3. Sub-cantilever region CA3 is connected to the mirror region MR via the connecting region SPA1. Sub-cantilever region CA1 is connected to the frame region FR. Sub-cantilever region CA2 connects sub-cantilever region CA1 to sub-cantilever region CA3. Each of sub-cantilever regions CA1 and CA2 has two electrodes 152 and 154, wherein the electrodes 152 of sub-cantilever regions CA1 and CA2 are electrically connected to each other, and the electrodes 154 of sub-cantilever regions CA1 to CA3 are electrically connected to each other. With this configuration, a large vertical displacement is provided by accumulating each bit displacement. Electrodes 152 and 154 can extend from the cantilever region CA to the frame region FR, thereby serving as conductive paths / pads for electrical connections.

[0070] Similarly, in this embodiment, the cantilever region CA' has sub-cantilever regions CA1' to CA3'. Sub-cantilever region CA3' is connected to the mirror region MR via the connection region SPA1. Sub-cantilever region CA1' is connected to the frame region FR. Sub-cantilever region CA2' connects sub-cantilever region CA1' to sub-cantilever region CA3'. Each of the sub-cantilever regions CA1' and CA2' has two electrodes 152 and 154, wherein the electrodes 152 of the sub-cantilever regions CA1' and CA2' are electrically connected to each other, and the electrodes 154 of the sub-cantilever regions CA1' to CA3' are electrically connected to each other. With this configuration, a large vertical displacement is provided by accumulating each bit displacement. Electrodes 152 and 154 can extend from the cantilever region CA' to the frame region FR, thereby serving as conductive paths / pads for electrical connections.

[0071] Similarly, in this embodiment, the cantilever region CB has sub-cantilever regions CB1 to CB3. Sub-cantilever region CB3 is connected to the mirror region MR via the connection region SPB1. Sub-cantilever region CB1 is connected to the frame region FR. Sub-cantilever region CB2 connects sub-cantilever region CB1 to sub-cantilever region CB3. Each of sub-cantilever regions CB1 and CB2 has two electrodes 152 and 154, wherein the electrodes 152 of sub-cantilever regions CB1 and CB2 are electrically connected to each other, and the electrodes 154 of sub-cantilever regions CB1-CB3 are electrically connected to each other. With this configuration, a large vertical displacement is provided by accumulating each bit displacement. Electrodes 152 and 154 can extend from the cantilever region CB to the frame region FR, thereby serving as conductive paths / pads for electrical connections.

[0072] Similarly, in this embodiment, the cantilever region CB' has sub-cantilever regions CB1' to CB3'. Sub-cantilever region CB3' is connected to the mirror region MR via the connection region SPB1'. Sub-cantilever region CB1' is connected to the frame region FR. Sub-cantilever region CB2' connects sub-cantilever region CB1' to sub-cantilever region CB3'. Each of the sub-cantilever regions CB1' and CB2' has two electrodes 152 and 154, wherein the electrodes 152 of the sub-cantilever regions CB1' and CB2' are electrically connected to each other, and the electrodes 154 of the sub-cantilever regions CB1' to CB3' are electrically connected to each other. With this configuration, a large vertical displacement is provided by accumulating each bit displacement. Electrodes 152 and 154 can extend from the cantilever region CB' to the frame region FR, thereby serving as conductive paths / pads for electrical connections. Different voltages can be applied to the electrodes 152 / 154 of the four cantilever regions CA, CB, CA', and CB' for individual operation and control. Other details of this embodiment are similar to those described above, and therefore will not be repeated here.

[0073] Figure 11A and Figure 11B These are top and bottom views of a MEMS device according to some embodiments of this disclosure. The details of this embodiment are similar. Figures 1A to 1C The difference lies in the details described above, where the impact buffer areas SB1 and SB2 are omitted in this embodiment (see [link to documentation]). Figures 1A to 1C Other details of this embodiment are similar to those described above, and therefore will not be repeated here.

[0074] Figure 12A and Figure 12B These are top and bottom views of a MEMS device according to some embodiments of this disclosure. The details of this embodiment are similar. Figures 1A to 1CThe difference lies in the details described above, where openings O2 and O3 in this embodiment do not extend to the first cantilever region CA and the second cantilever region CB. Therefore, the first cantilever region CA can be a complete cantilever connecting the frame region FR and the connecting regions SPA1 and SPA2. Furthermore, the second cantilever region CB can be a complete cantilever connecting the frame region FR and the connecting regions SPB1 and SPB2. Figures 1A to 1C As shown, the first cantilever region CA and the second cantilever region CB may not have multiple sub-cantilever regions. With this configuration, the first cantilever region CA and the second cantilever region CB have higher strength, thus allowing for higher resonant frequencies. Other details of this embodiment are similar to those described above, and therefore will not be repeated here.

[0075] Based on the foregoing discussion, it is evident that the present disclosure offers advantages. However, it should be understood that other embodiments may provide additional advantages, and not all advantages are necessarily disclosed herein, nor are the specific advantages of all embodiments required. One advantage is that the multi-cantilever actuator provides a large output displacement for the torsional mode of the scanning mirror, thereby achieving a good optical scanning angle. Another advantage is that the multi-cantilever actuator enhances the stability of the device and avoids lateral movement problems. Yet another advantage is that the design of the impact buffer increases stability outside the reflector surface and reduces swaying. A further advantage is that the signal-to-noise ratio is sufficiently high for long-distance detection, the resonant frequency is sufficiently high for faster scanning speeds, and it can withstand vibrations from the working environment.

[0076] In some embodiments of this disclosure, the microelectromechanical system (MEMS) device includes a mirror structure, a frame, a first cantilever, and a second cantilever. The mirror structure is suspended in the frame by the first and second cantilever arms. The first cantilever includes a first sub-cantilever connected to the frame; a second sub-cantilever connected to the mirror structure; and a third sub-cantilever connecting the first and second sub-cantilever arms. Each of the first and third sub-cantilever arms includes a first bottom electrode; a first piezoelectric layer on the first bottom electrode; and a first top electrode and a second top electrode on the first piezoelectric layer, wherein the first and second top electrodes are separated from each other.

[0077] In some embodiments, the microelectromechanical system device further includes an impact buffer connecting the mirror structure and the frame, wherein the impact buffer extends along a rotation axis of the mirror structure.

[0078] In some embodiments, the impact buffer is located between the second cantilever and the first cantilever.

[0079] In some embodiments, the angle between the longitudinal direction of the first sub-cantilever and the direction perpendicular to the rotation axis of the mirror structure is 0 to 40 degrees in a top view.

[0080] In some embodiments, the angle between the longitudinal direction of the third sub-cantilever and the direction perpendicular to the rotation axis of the mirror structure is 0 to 40 degrees in a top view.

[0081] In some embodiments, the second sub-cantilever includes a third top electrode electrically connected to the first top electrode.

[0082] In some embodiments, the second sub-cantilever extends across the mirror structure in a direction parallel to a rotation axis of the mirror structure in a top view.

[0083] In some embodiments, the first cantilever further includes a fourth sub-cantilever and a fifth sub-cantilever. The fourth sub-cantilever is connected to the frame. The fifth sub-cantilever connects the second sub-cantilever and the fourth sub-cantilever, wherein each of the fourth and fifth sub-cantilever includes a second bottom electrode, a second piezoelectric layer, a third top electrode, and a fourth top electrode. The second bottom electrode is electrically connected to the first bottom electrode. The second piezoelectric layer is located on the second bottom electrode, wherein the second piezoelectric layer is connected to the first piezoelectric layer. The third and fourth top electrodes are located on the second piezoelectric layer, wherein the third and fourth top electrodes are separated from each other and are electrically connected to the first and second top electrodes, respectively.

[0084] In some embodiments, the mirror structure includes a reflector that is laterally aligned with the first top electrode and the second top electrode in a cross-sectional view.

[0085] In some embodiments disclosed herein, the MEMS device includes: a mirror structure; a frame; a first impact buffer and a second impact buffer connecting the mirror structure and the frame, wherein the first impact buffer and the second impact buffer extend along the rotation axis of the mirror structure; a first cantilever and a second cantilever, wherein the mirror structure is suspended in the frame by the first cantilever and the second cantilever; a first connecting spring adjacent to the first impact buffer and connecting the first cantilever to the mirror structure; and a second connecting spring adjacent to the first impact buffer and connecting the second cantilever to the mirror structure, wherein the first connecting spring and the second connecting spring are spaced apart from the rotation axis of the mirror structure in the top view.

[0086] In some embodiments of this disclosure, the microelectromechanical system device includes: a mirror structure; a frame; a first cantilever and a second cantilever, wherein the mirror structure is suspended in the frame by the first cantilever and the second cantilever, each of the first cantilever and the second cantilever including a bottom electrode, a piezoelectric layer above the bottom electrode, and a first top electrode and a second top electrode above the piezoelectric layer; a first connecting spring connecting the first cantilever to the mirror structure; and a second connecting spring connecting the second cantilever to the mirror structure.

[0087] In some embodiments, the microelectromechanical system device further includes a first impact buffer and a second impact buffer, connecting the mirror structure and the frame, wherein the first impact buffer and the second impact buffer extend along a rotation axis of the mirror structure.

[0088] In some embodiments, the first connecting spring and the first impact buffer are laterally aligned in a top view, and the second connecting spring and the first impact buffer are laterally aligned in the top view.

[0089] In some embodiments, the width of the first impact buffer and the second impact buffer increases from the mirror structure to the frame.

[0090] In some embodiments, the first cantilever has a plurality of first sub-cantilevers, and the width of the first connecting spring is smaller than the width of the first sub-cantilevers.

[0091] In some embodiments, the second cantilever has a plurality of second sub-cantilevers, and the width of the second connecting spring is smaller than the width of the second sub-cantilevers.

[0092] In some embodiments, in a top view, the length of the first top electrode measured along a direction parallel to a rotation axis of the mirror structure is greater than the length of the mirror structure measured along the rotation axis of the mirror structure.

[0093] In some embodiments, the first connecting spring and the second connecting spring do not include the first top electrode, the second top electrode, the piezoelectric layer, and the bottom electrode.

[0094] In some embodiments of this disclosure, a method for forming a MEMS device is provided. The method includes: depositing a first electrode layer on a semiconductor substrate; depositing a piezoelectric layer on the first electrode layer; depositing a second electrode layer on the piezoelectric layer; patterning the second electrode layer into at least a first electrode, a second electrode, and a mirror; and etching the piezoelectric layer and the first electrode layer to form at least a first cantilever region, a second cantilever region, a mirror region, and a frame region, wherein the mirror region is suspended through the first cantilever region, the second cantilever region, and the frame region; the first cantilever region includes the first cantilever region; a second sub-cantilever region, wherein each of the first and second sub-cantilever regions includes the first electrode and the second electrode; and a third sub-cantilever region, wherein the third sub-cantilever region is connected to the mirror region.

[0095] In some embodiments of this disclosure, a method for forming a MEMS device is provided. The method includes: depositing a bottom electrode layer over a semiconductor substrate; depositing a piezoelectric layer over the bottom electrode layer; depositing a top electrode layer over the piezoelectric layer; patterning the top electrode layer as at least a first top electrode, a second top electrode, and a mirror; and etching the piezoelectric layer and the bottom electrode layer to form at least a first cantilever region, a second cantilever region, a mirror region, and a frame region, wherein the mirror region is suspended through the first cantilever region, the second cantilever region, and the frame region, and the first cantilever region includes: a first sub-cantilever region; a second sub-cantilever region, wherein each of the first sub-cantilever region and the second sub-cantilever region includes the first top electrode and the second top electrode; and a third sub-cantilever region, wherein the third sub-cantilever region connects to the mirror region.

[0096] In some embodiments, the method further includes etching a back side of a substrate of the semiconductor substrate to form a frame above the frame region and a rib structure above the mirror region.

[0097] In some embodiments, the method further includes providing different voltages to the first top electrode and the second top electrode respectively, so that the reflector has a target scanning angle.

[0098] In some embodiments of this disclosure, the microelectromechanical system (MEMS) device includes a substrate, a bottom electrode layer, a piezoelectric layer, a first top electrode, a second top electrode, and a mirror above the piezoelectric layer. The substrate has a first cantilever region, a second cantilever region, a mirror region, and a frame region, wherein the mirror region is suspended by the first cantilever region, the second cantilever region, and the frame region. The first cantilever region includes a first sub-cantilever region, a second sub-cantilever region, and a third sub-cantilever region, wherein the third sub-cantilever region connects to the mirror region. The bottom electrode layer is above the substrate. The piezoelectric layer is above the bottom electrode layer. The first top electrode, the second top electrode, and the mirror are above the piezoelectric layer. The mirror is located in the mirror region. A first portion of the first top electrode and a first portion of the second top electrode are located in the first sub-cantilever region, and a second portion of the first top electrode and a second portion of the second top electrode are located in the second sub-cantilever region.

[0099] In some embodiments, the microelectromechanical system device further includes a frame and rib structures. The frame is located on a back side of the substrate and in the frame region. The rib structures are located on the back side of the substrate and in the mirror region.

[0100] The foregoing outlines features of several embodiments to enable those skilled in the art to better understand the various aspects of this disclosure. Those skilled in the art should understand that this disclosure can be readily used as a basis for designing or modifying other processes and structures to achieve the same objectives and / or advantages as the embodiments described herein. Those skilled in the art should also recognize that these equivalent constructions do not depart from the spirit and scope of this disclosure, and that various changes, substitutions, and modifications can be made to these equivalent constructions without departing from the spirit and scope of this disclosure.

Claims

1. A microelectromechanical system (MEMS) device, characterized in that, Include: A mirror-like structure; A framework; and A first cantilever and a second cantilever, wherein the mirror structure is suspended in the frame by the first cantilever and the second cantilever, and the first cantilever includes: A first cantilever is connected to the frame; A second cantilever, connected to the mirror structure; and A third sub-cantilever connecting the first sub-cantilever and the second sub-cantilever, wherein each of the first sub-cantilever and the third sub-cantilever comprises: A first bottom electrode; A first piezoelectric layer is located on the first bottom electrode; and A first top electrode and a second top electrode are located on the first piezoelectric layer, wherein the first top electrode and the second top electrode are separated from each other.

2. The microelectromechanical system device as described in claim 1, characterized in that, Further includes: An impact buffer is provided to connect the mirror structure to the frame, wherein the impact buffer extends along a rotation axis of the mirror structure.

3. The microelectromechanical system device as described in claim 2, characterized in that, The impact buffer is located between the second cantilever and the first cantilever.

4. The microelectromechanical system device as described in claim 1, characterized in that, The mirror structure includes a reflecting mirror.

5. The microelectromechanical system device as described in claim 1, characterized in that, The second sub-cantilever includes a third top electrode that is electrically connected to the first top electrode.

6. A microelectromechanical system (MEMS) device, characterized in that, Include: A mirror-like structure; A framework; A first cantilever and a second cantilever, wherein the mirror structure is suspended in the frame by the first cantilever and the second cantilever, each of the first cantilever and the second cantilever includes a bottom electrode, a piezoelectric layer above the bottom electrode, and a first top electrode and a second top electrode above the piezoelectric layer; A first connecting spring connects the first cantilever to the mirror structure; and A second connecting spring connects the second cantilever to the mirror structure.

7. The microelectromechanical system device as described in claim 6, characterized in that, Also includes: A first impact buffer and a second impact buffer are provided to connect the mirror structure and the frame, wherein the first impact buffer and the second impact buffer extend along a rotation axis of the mirror structure.

8. The microelectromechanical system device as described in claim 7, characterized in that, The first cantilever has multiple first sub-cantilevers, and the width of the first connecting spring is smaller than the width of the first sub-cantilevers.

9. A microelectromechanical system (MEMS) device, characterized in that, Include: A substrate has a first cantilever region, a second cantilever region, a mirror region and a frame region, wherein the mirror region is suspended through the first cantilever region, the second cantilever region and the frame region, and the first cantilever region includes a first sub-cantilever region, a second sub-cantilever region and a third sub-cantilever region, wherein the third sub-cantilever region is connected to the mirror region. A bottom electrode layer is located above the substrate; A piezoelectric layer is placed above the bottom electrode layer; as well as A first top electrode, a second top electrode, and a reflector are located above the piezoelectric layer, wherein the reflector is located in the mirror region, a first portion of the first top electrode and a first portion of the second top electrode are located in the first sub-cantilever region, and a second portion of the first top electrode and a second portion of the second top electrode are located in the second sub-cantilever region.

10. The microelectromechanical system device as described in claim 9, characterized in that, Further includes: A frame, located on a back side of the substrate and within the frame region; and A rib-like structure is located on the back side of the substrate and in the mirror area.

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